547. Number of Provinces

Medium
There are n cities. Some of them are connected, while some are not. If city a is connected directly with city b, and city b is connected directly with city c, then city a is connected indirectly with city c.
A province is a group of directly or indirectly connected cities and no other cities outside of the group.
You are given an n x n matrix isConnected where isConnected[i][j] = 1 if the ith city and the jth city are directly connected, and isConnected[i][j] = 0 otherwise.
Return the total number of provinces.
Example 1:
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Input: isConnected = [[1,1,0],[1,1,0],[0,0,1]]
Output: 2
Example 2:
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Input: isConnected = [[1,0,0],[0,1,0],[0,0,1]]
Output: 3
Constraints:
  • 1 <= n <= 200
  • n == isConnected.length
  • n == isConnected[i].length
  • isConnected[i][j] is 1 or 0.
  • isConnected[i][i] == 1
  • isConnected[i][j] == isConnected[j][i]

解題

func findCircleNum(isConnected [][]int) int {
parent := make([]int, len(isConnected))
for i:=0; i<len(parent); i++ {
parent[i] = i
}
​
for i:=0; i<len(isConnected); i++ {
for j:=i + 1; j<len(isConnected[0]); j++ {
if isConnected[i][j] == 1 {
union(i, j, parent)
}
}
}
m := make(map[int]bool)
for _, v := range parent {
m[findRoot(parent, v)] = true
}
​
return len(m)
}
​
func union(i, j int, parent []int) {
fi, fj := findRoot(parent, i), findRoot(parent, j)
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if fi > fj {
parent[fi] = fj
} else if fi < fj {
parent[fj] = fi
}
}
​
func findRoot(parent []int,n int) int {
if parent[n] == n {
return n
}
return findRoot(parent, parent[n])
}
​